The concept of applying drive-by-wire system for constructing an overall electric scheme, being feasible to the related applications, is mainly to replace mechanical elements of brake devices, which may employ oil pressure control and gears such as a fuel pedal and a steering wheel, by an electronic driving approach. SKF Co. and Bertone jointly developed a prototype concept car named FILO in 2001 that adopted the drive-by-wire technique with an integrated system control unit. As electronic signal transmission is more sensitive than mechanical operation and conforming the electronically controlled trend for the improvement of development for the conventionally mechanical type motion control, in the event of an accident, a corresponding passive protection measure may be taken for an integration driving, so called drive-by-wire, in an easier way. However, the market for this opinion is not mature for being still in lack of acceptable response capability about the safety operation mechanism of that type of vehicles. It is obviously that needing more research efforts involved for improving the safety acceptability. No doubt that the consideration for the brake function plays the important role for the techniques development.
Energy recycling and recovery related techniques and applications have been generally realized in the prior art. For instance, U.S. Pat. No. 6,202,782 to Hatanaka issued Mar. 20, 2001, disclosed a technique for recovering thermal energy that used two flywheels to transform mechanical energy into electric energy and store the energy in a battery to design the operation procedures for reusing the braking energy for a hybrid vehicle propulsion system. To increase the braking power without exceeding a predetermined braking power and focus on the action apparatus used in electric motor vehicles was addressed in U.S. Pat. No. 5,377,791 to Kawashima et al. issued Jan. 3, 1995. However, the method for the recovery energy applying to do the brake operation was not elaborated herein. The mechanical structure needed to actuate the brake function also took a greater proportion in the system design. The prior art described in patents does not explicitly cover both the operation consideration and steps related to the method and apparatus for design concept about how to utilize the recovery braking energy with/without energy feedback flow and the auxiliary energy source is also taken into account to improve the brake effectiveness. In fact, an electric-driven brake device is still the apparently technical bottleneck for the drive-by-wire vehicle system development and has to be explored for breakthrough.
The United States Environmental Protection Agency (US-EPA) has defined Federal Test Procedure 75 (FTP75), targeting an electrical vehicle (EV) that regulates brake test mechanisms and processes, including frequency/speed of rotation, operation ratio range of torque, and so forth. It can be clearly observed that while testing the present electrical vehicles according to FTP75, the ratio of energy deployment and operation under the brake conditions is still excessively high. The brake performance and reliability are no doubt the important examination factors needed to put to the test. All this mentioned above indicates that while the present vehicles have progress on the issues of energy conservation and recovery energy application, there are still no overall effective solutions to solve the problem of energy consumption during braking process, and no verbosity the more challengeable research topic for the development of present electrical vehicles.
For the vehicle body designed with mechanical transmission, the braking mechanism has even a greater field to be discussed for system performance upgrading. Conventional brake operation based on the mechanical transmission is usually accomplished through plate brakes and speed reducing mechanisms. For simplicity, they generally can be divided into drum type brakes and disk type brakes. The ordinary vehicles mostly adopt the design of disk type brakes on the front wheels to perform the brake action and drum type brakes on the rear wheels as well. The function of the drum type brake is acting like a clip, which is spread to increase friction effect on the brake linings to reduce the speed of the vehicle. As for the disk type brake, it uses a clip-like component to clamp symmetrical disk mounted on the rotation axle to achieve the brake function. The disk type brake can stop the vehicles at a shorter distance than the drum type brake, thus is safer in this discussion opinion. Besides, some vehicles are also coupled with a brake-locking prevention function, such as an anti-brake system (ABS), to improve safety. However, these mechanically dominated brake devices still require brake oil and some pollutants for the operation. In terms of energy deployment, converting kinetic energy to thermal energy involves heat dissipation. The temperature under the heat reaction status could reach several hundred degrees Celsius. This mechanical mechanism technique still needs further improvement in the opinion of environmental protection and energy utilization, especially for the research of drive-by-wire vehicles. Moreover, the service life and severe life cycle of the conventional brake systems is not predictable because the affecting factors, which can be focus on wearing and aging, deteriorate systems during randomly occurred brake operation. Besides of that, the maintenance for safety concern also makes it relatively expensive to replace the brake elements while considering the cost in specific time intervals.
The feasibility to operate the switched reluctance (SR) machines, the electrical machines with double-salience that without winding in its rotor, and owning the advantages of high power density, high robustness with rigid structure and temperature allowance, simple structure for low materials and manufacturing cost, wide speed range, and so on, is proved under assigned brake function in published lectures. In IEEE Transactions on Magnetics, 39(5), 3253 (2003), Osamu Ichinokura et al. have developed the evaluation simulation model of SR machines, including the dynamic behavior calculation for generator utilization, being useful for analysis and design. The study has also shown that SR machines can meet the requirements for propulsion application using microcontroller-based drives by Robert B. Inderka et al. published in IEEE Transaction on Industrial Electronics, 49(1), 48 (2002). Hereafter, to apply the high environmental robustness reluctance force production source to achieve the objectives, which can construct the drive-by-wire vehicles concrete concept and enlarge the reluctance force application fields, both by the means of the energy reused concept based on the transiently required reverse reluctance force supplying for brake function is the original invention motivation.